This invention relates to a drive chain and more particularly to a bicycle roller chain that prevents the pin connection from rupturing under lateral forces.
It is known in the art to provide a roller chain that has a plurality of interconnected chain links that form a drive element between two gear wheels to drive a bicycle. For example, a French patent, FR2753512, discloses a chain for bicycles, which includes chain links having outer link plates and inner link plates. Each plate has holes for receiving pins that connect the links together. '512 discloses a lightweight drive chain while still providing adequate load bearing capacity. The weight of the chain is lightened in two ways. First, the outer link plate point is provided with an opening disposed in the middle of the outer link plate which also reduces the external contour of the outer link plate. Second, the pin is made hollow. The pin is made from tube stock and is pressed into the holes of the outer link plates and inner link plates. After being pressed into the holes, the pin is riveted to increase its press fit in the outer link plate, resulting in a slight expansion of the hole at the outer edge of the hole in the outer link plate. Such an expansion usually occurs, whether the pin is made from solid stock or tube stock because of the act of riveting it.
A problem associated with riveting the pins is that the connection between the pins and the link plates may ruptured under lateral forces that occur when changing from a first gear to a second gear which is not aligned with the first gear. Due to these forces, the riveted end of the pin is pulled through the hole of the outer link plate. Thus, merely riveting the pin in the outer link plate does not prevent the destruction of the roller chain under high operating loads. Therefore, there is a need for a roller chain having a configuration that prevents the end of the pin from being pulled through the hole of the outer link plate.
Further, when designing a roller chain to be used with a gear set on the rear axle of the bicycle, it is important that the configuration of the roller chain allows the smallest possible interval between the gears in order to accommodate a maximum number of sprockets on the rear axle. This can be accomplished by having components that do not project over the external surface of the roller chain, which is essentially defined by the outer surface of the outer link plate. One component that usually protrudes beyond the outer surface of the outer link plates is the pin. The pin usually has an edge that projects beyond the external surface of the outer chain link. Further, the edges of the pin may get caught on the toothing of an adjacent gear, especially a larger gear, and may give rise to unintended gear shifts or noises.
There is a need for a roller chain that has a configuration that prevents the rupture of the pin connection under lateral forces and has a narrow design to permit a maximum number of chain sprockets on the rear axle of the bicycle.